1. Field of the Invention
The invention relates in general to heat exchangers, to electrical apparatus having heat exchangers, and methods of constructing same, and more specifically to heat exchangers suitable for electrical inductive apparatus, such as electrical distribution and power transformers.
2. Description of the Prior Art
Electrical apparatus which includes heat generating means disposed in a tank with a fluid cooling dielectric, liquid, vapor or gas, including liquids such as mineral oil, vaporizable liquids such as perchloroethylene, and gasses such as SF6 gas, must exchange the heat built up in the tank with the atmosphere. When the tank itself does not provide the requisite heat exchange surface, the fluid cooling dielectric is circulated through heat exchangers which are connected to the tank. The flow may be natural thermal siphon, or forced via suitable pumping means, as desired.
The hermetically sealed tank of electrical apparatus, such as electrical distribution and power transformers, and heat exchanger apparatus associated with the tank, are subjected to relatively high pressures during normal thermal cycling. In addition to withstanding normal pressures, the tank and associated heat exchanger apparatus must be able to withstand extremely high pressures for short periods of time without rupturing the tank or heat exchanger apparatus, which pressures may be created by abnormal conditions, such as internal faults.
In the prior art, the tanks and associated heat exchanger apparatus are constructed of steel having the requisite thickness dimensions to accommodate the pressure tests prescribed by the manufacturer and industry standards.